Police in the US state of Texas are negotiating with a man who has taken several hostages at a synagogue in the town of Colleyville.
One hostage was freed late on Saturday, police said. He was unharmed and no other injuries have been reported, reports BBC.
The synagogue's service was being streamed online when the incident began. An angry man could be heard saying he did not want to hurt anyone.
Police deployed special weapons teams and local people were evacuated.
Four people are believed to have been taken hostage originally including the synagogue's rabbi, according to US media reports.
One law enforcement official told the Associated Press that the man has claimed to be armed, but they have been unable to confirm whether he is.
FBI crisis negotiators are in contact with the hostage-taker.
President Joe Biden, meanwhile, has been briefed about the developing situation.
The incident began at around 11:00 local time (16:00 GMT) on Saturday when police were called to the Congregation Beth Israel synagogue. People were evacuated from the area shortly after.
A live stream of the Shabbat morning service on Facebook captured audio of a man talking loudly. He could be heard saying: "You get my sister on the phone" and "I am gonna die".
He was also heard saying: "There's something wrong with America." The feed has since been taken down.
The hostage-taker was also heard demanding the release of Aafia Siddiqui, a Pakistani neuroscientist who is currently serving an 86-year prison term in the US, law enforcement officials told local media.
Siddiqui was convicted of trying to kill US military officers while in custody in Afghanistan.
Barry Klompus, a member of the congregation since it opened in 1999, said he had been told about the incident by another member and had quickly turned to the live feed until it was taken down.
"It was horrible listening and watching, and it's that much more horrible not knowing," he told Reuters news agency.
Victoria Francis told the Associated Press that she heard the man rant against America and claim he had a bomb during the live stream. "It's a scary situation. I'm hopeful it ends the best way it can," she said.